Dear Helen: I have some well-established perennial plantings and wonder when and how often they should be divided. Can you comment particularly on Lenten rose, hostas, border sedums and bearded irises?
L. P.
Lenten rose (Heleborus hybridus) rarely needs dividing and replanting. In fact, the plants manifest a marked resentment if they are disturbed once they are established. Do remove old foliage in winter though, and spread a clean mulch around the plants.
Hostas are similar. They can be divided in spring or early autumn, but they commonly last for many years before showing signs of decline. I’ve had several hostas in the same pots for years.
The taller types of sedum, commonly referred to as border sedums, vary in their need for division. I have some, for instance the old ‘Autumn Joy,’ that rarely require splitting, and other, newer forms that seem to require division every second year. Keeping the soil a little on the lean and dry side helps to restrain their exuberance and need for dividing.
Watch for bare areas in the centre of a perennial clump. That suggests it’s time for lifting the clump and replanting the youngest portions from its outer parts. Other indications are plants that have reached unwieldy proportions and ones that no longer bloom well.
Most perennials can be divided in spring or early autumn, with some exceptions. Lift and divide peony clumps as the foliage begins dying back in October, lilies mid to late fall. For plants such as sedums that prefer a dryish soil, spring is the safer time to divide and replant.
Dear Helen: I am fond of dahlias and delight in their diversity of flower form and colour. In past gardens, I have grown mainly the large dinner-plate-size types, but now I’m in a patio home where I’d have to grow the plants in containers. Is this possible?
C.A.
Many dahlias are highly recommended for growing in containers. Some of the bronze-leaved plants, such as the orange-flowered ‘City of Alkmaar’ and rose ‘City of Leiden’ grow 60-centimetres tall and would be lovely in containers with a skirting of spreading petunias planted around the pot edge.
Some local garden centres will have these dahlias, along with “Gallery” dahlias that grow just 35 to 45 cm tall. Look too among “novelty” dahlias such as the 40-cm, white-and-red ‘Fire and Ice’.
Ferncliff Gardens is another source for a broad range of dahlias. They have a selection of low-growing bedding dahlias that includes ‘Park Princess,’ my father’s favourite dahlia. ferncliffgardens.com.
In its current catalogue, a wholesale supplier to our local garden centres recommends container cultivation even for some of its taller, large-flowered dahlias. Check labels on the roots for this information.
Use a pot about 35 cm wide for smaller dahlias and consider adding complementary underplantings, such as spreading perunias and calibrachoas, colourful heucheras or weeping sedges (Carex).
As you pot a tuberous root that will produce a tall plant, insert a sturdy stake before filling the pot, while the root is still in view, to avoid stabbing it.
Dahlias can be trained for a desired effect. Pinching back developing stems once or twice as they elongate will create a broader, bushier plant. Or, leave the stems alone for a looser, taller effect, which is probably the better option if underplantings are used. As summer progresses, some of a dahlia’s lower leaves can be removed to enhance the underplanting’s exposure to light.
Potted dahlias will give a long season of colour, until frost in the fall, if the soil is kept moist and faded flowers are removed.
GARDEN EVENTS
Lily meeting. The Victoria Lily Society will meet this evening at 7:30 in the Salvation Army Citadel, Douglas and McKenzie. Guest speaker Malcolm Ho-You will give a presentation on peonies. Visitors are welcome.
Orchid show and sale. The Victoria Orchid Society is presenting its annual Show and Sale on Saturday, 9 a.m. to 5 p.m. and Sunday, 11:30 a.m. to 4 p.m., in Our Lady of Fatima Hall, 4635 Elk Lake Road, across from the Commonwealth Pool. Cost of admission is $7 for adults; $6 for students and seniors. Children under 12 accompanied by an adult are admitted at no cost. Proceeds are to be shared with the Children’s Health Foundation of Vancouver Island. Parking is free and plentiful. victoriaorchidsociety.com.
